Security systems are used to protect life and property. A typical security system includes a control panel and multiple sensors. The control panel includes a transceiver for transmitting and receiving data from the sensors. The sensors include a transceiver for transmitting and receiving data from the control panel. The transceivers are adapted for spread spectrum (frequency hopping communication). These transceivers operate on a fixed set of channels.
A pseudorandom channel-hopping order is designed into a communication protocol so that all the radio traffic is spread evenly across all of the defined channels within the system. The list of channels and the hopping sequence in which they are used, are specified in a product's design and form part of the type approval requirements for the device.
The sensors also include a battery. The sensors are typically asleep in a standby mode for most of the time to save battery power. The sensors wake up infrequently to send supervisory or alarm messages. In general, it is either cost- or power-prohibitive for the sensor to maintain an internal timebase with sufficient accuracy that it can remain in synchronization with the control panel during sleep mode. Therefore, at each wakeup, the sensor must go through a negotiation phase to synchronize its position in the pseudorandom hop sequence with the transceiver in the control panel. This negotiation phase takes a considerable time, which impacts battery life of the sensor.
Currently, the control panel transmits a beacon containing a time reference to the sensor for synchronization. The sensors use the time reference to synchronize the channel with the control panel. However, FCC regulations limit the transmissions of the beacon in such a way that a potentially lengthy negotiation sequence is necessary for the control panel and the peripheral to be sure they are synchronized correctly.